For improved television transmission systems, it has been shown to be desirable, particularly in view of the preference of the general public, to increase the aspect ratio of a television receiver from 4:3, as found in present standard receivers, to 16:9 (i.e., the recommended aspect ratio of future HDTV standards) or 5:3 without losing compatibility with existing television standards (PAL, NTSC, SECAM). To achieve this, it is suggested in German patent DE 3840054 to separate, at the transmitter, every fourth line of the picture signal, and to spatially compress or interpolate the remaining lines in the correct spatial position. The separated lines are added, directly or in scrambled form, into vacated spatial areas created by the spatial compression along upper and lower edges of the picture. The resulting picture signal is then transmitted in coded form. The original picture signal with a 16:9 or 5:3 aspect ratio is reconstructed from a received decoded picture signal. Specifically, the separated lines (i.e., every fourth line) disposed in the upper and lower picture edge areas are, after descrambling, inserted among the remaining spatially decompressed (expanded) lines in the correct line sequence. Upon reproducing the received signal by a current (state-of-the-art) 4:3 aspect ratio television receiver, the scrambled lines added along the upper and lower picture edge areas are reproduced as quasi-noise bands (bars) which can be disturbing to a viewer.
It is an object of the invention to develop a system of the aforementioned type such that, upon reproduction of the picture signal by a conventional 4:3 television receiver, the upper and lower edge areas of the picture appear as essentially consistent picture areas.